Patent Application
20050197626
This invention relates generally to improvements in fluid reservoirs. More specifically, this invention relates to an improved fluid reservoir and piston for use in combination with external infusion pumps such as those used for controlled delivery of medication to a patient.
Infusion pump devices and systems are relatively well-known in the medical arts, for use in delivering or dispensing a prescribed medication such as insulin to a patient. In one form, such devices comprise a relatively compact pump housing adapted to receive a syringe or reservoir carrying a prescribed medication for administration to the patient through infusion tubing and an associated catheter or infusion set.
The infusion pump includes a small drive motor connected via a lead screw assembly for motor-driven advancement of a reservoir piston to administer the medication to the user. Programmable controls can operate the drive motor continuously or at periodic intervals to obtain a closely controlled and accurate delivery of the medication over an extended period of time. Such infusion pumps are used to administer insulin and other medications, with exemplary pump constructions being shown and described in U.S. Pat. Nos. 4,562,751; 4,678,408; 4,685,903; 5,080,653 and 5,097,122, which are incorporated by reference herein.
Infusion pumps of the general type described above have provided significant advantages and benefits with respect to accurate delivery of medication or other fluids over an extended period of time. The infusion pump can be designed to be extremely compact as well as water resistant, and may thus be adapted to be carried by the user, for example, by means of a belt clip or the like. As a result, important medication can be delivered to the user with precision and in an automated manner, without significant restriction on the user's mobility or life-style, including in some cases the ability to participate in water sports.
These pumps often incorporate a drive system which uses a lead screw coupled to motors. The motors can be of the DC, stepper or solenoid varieties. These drive systems provide an axial displacement of the syringe or reservoir piston thereby dispensing the medication to the user. Powered drive systems are advantageous since they can be electronically controlled to deliver a predetermined amount of medication by means well known in the art.
In the operation of these pump systems, the reservoir piston will be fully advanced when virtually all of the fluid in the reservoir has been dispensed. Correspondingly, the axial displacement of the motor lead screw is also typically fully displaced. In order to insert a new reservoir which is full of fluid, it is necessary to restore the lead screw to its original position. Thus the lead screw will have to be rewound or reset.
DC motors and stepper motors are advantageous over solenoid motors in that the former are typically easier to operate at speeds that allow rewinding the drive system electronically. Solenoid based drive systems, on the other hand, often must be reset manually, which in turn makes water resistant construction of the pump housing more difficult.
Lead screw drive systems commonly use several gears which are external to the motor.
Should an occlusion arise in the infusion set 106 tubing, a back pressure will build up in the reservoir 105 as the piston 104 attempts to advance. The force of the piston 104 pushing against the increased back pressure will result in an axial force of the lead screw 102 driving against the detector 108. If the detector 108 is a pressure limit switch, then an axial force that exceeds the set point of the pressure limit switch 108 will cause the switch to close thus providing an electrical signal through electrical leads 109 and to the system's electronics. This, in turn, can provide a system alarm. The entire assembly can be contained in a water resistant housing 107.
As previously noted, these lead screw drive systems use gears which are external to the motor. The gears are in combination with a lead screw with external threads which are used to drive the reservoir's piston. This external arrangement occupies a substantial volume which can increase the overall size of the pump. Moreover, as the number of drive components, such as gears and lead screw, increases, the torque required to overcome inherent mechanical inefficiencies can also increase. As a result, a motor having sufficient torque also often has a consequent demand for increased electrical power.
Yet another known drive is depicted in
As is more clearly shown in
While the in-line drive system of
Moreover the drive screw 305 and piston head 304 of
The design of
The construction of pumps to be water resistant can give rise to operational problems. As the user travels from various elevations, such as might occur when traveling in an air plane, or as the user engages in other activities which expose the pump to changing atmospheric pressures, differential pressures can arise between the interior of the air tight/water-resistant pump housing and the atmosphere. Should the pressure in the housing exceed external atmospheric pressure, the resulting forces could cause the reservoir piston to be driven inward thus delivering unwanted medication.
Thus it is desirable to have an improved, compact, water resistant drive system which permits safe user activity among various atmospheric pressures and other operating conditions. Moreover it is desirable to have improved medication reservoir pistons for use with such drive systems.
It is an object of an embodiment of the present invention to provide an improved fluid reservoir, which obviates for practical purposes, the above mentioned limitations.
According to an embodiment of the present invention, an external infusion device for infusion of a fluid into a body from a reservoir includes a drive system, a housing, electronic control circuitry and at least one vent port. The drive system is operatively coupled with a reservoir to infuse a fluid into a body. The housing is adapted for use on an exterior of the body, and is sized to contain at least a portion of a reservoir. In addition, the drive mechanism is at least partially contained within the housing, and operatively couples with the at least a portion of a reservoir within the housing. Also, the housing is sized to be carried by a user without significant restriction on mobility. The electronic control circuitry is coupled to the drive system to control infusion of the fluid into the body. Moreover, the housing has at least one vent port that permits the passage of air into and out of the housing and inhibits the passage of liquids into the housing through the at least one vent port.
In additional embodiments, the at least one vent port further includes a hydrophobic material that permits the passage of air into and out of the housing and inhibits the passage of liquids into the housing through the at least one vent port. In further embodiments, the hydrophobic material is formed from PTFE and/or formed as sheet. In still further embodiments, the sheet of hydrophobic material is attached to the housing using adhesives, sonic welding, heat welding to cover the at least one vent port or is a label. In yet further embodiments, the hydrophobic material is pressed into the housing of the external infusion device, and may be pressed into a cavity in the housing that forms the at least one vent port, and the material may even be molded to fit the cavity in the housing.
In preferred embodiments, the hydrophobic material resists the passage of water, and the external infusion device is configured to infuse insulin. In addition, the housing and at least one vent port provide a water resistant structure that provides the user with the ability to participate in water sports. Moreover, the at least one vent port allows the air pressure within the housing to equalize with the air pressure outside of the housing.
An improved pump is provided with a reservoir for accommodation of a liquid and a movable piston for varying the size of the reservoir and adapted to discharge the liquid from the reservoir through the outlet. In a certain aspect of the present inventions, a plunger slide is releasably coupled with the movable piston and has at least two positions. A driving device, such as a motor, is operably coupled to a drive member, such as a drive screw. The motor is disposed in-line with the drive screw and the plunger slide. The drive screw is operably connected to the plunger slide and is disposed to be substantially enclosed by the plunger slide when it is in at least one position. The drive screw is adapted to advance the plunger slide in response to operation of the motor.
In one alternative, a housing for the reservoir, the movable piston, the plunger slide, the drive screw and the motor is provided along with a sealing device, such as an O-ring, that separates the portion of the housing which encloses the movable piston from the portion of the housing which encloses the drive screw and the motor.
In another preferred embodiment, a coupler is attached to the plunger slide. The coupler is removably attached to the movable piston to prevent separation of the movable piston from the plunger slide when the air pressure in the housing exceeds the pressure external to the water resistant housing.
In still another embodiment, the housing includes a vent port between the exterior and interior of the housing. The vent port contains a hydrophobic material or a relief valve, either of which will permit air to pass through the vent, but will prevent water from passing.
In another alternative, the driving device is a motor which is attached to the housing with a compliance mount. In another embodiment, the plunger slide comprises a telescoping lead screw formed from at least two segments.
In yet another embodiment, the pump includes a key which is coupled with the plunger slide and which is operable to permit movement of the plunger slide in the direction of the at least two positions but prevent movement of the plunger slide in any other direction.
An improved apparatus for dispensing a medication fluid is provided. This comprises a reservoir adapted to contain the fluid and a movable piston adapted to vary the size of the reservoir and to discharge the liquid from the reservoir through an outlet. In a certain aspect of the present inventions, the reservoir and piston are adapted for use with a pump drive system having a linear actuation member wherein the piston can be releasably coupled to the linear actuation member.
The piston comprises a first member adapted to be slidably mounted within the reservoir and to form at least part of a fluid-tight barrier therein. The first member has an external proximate side and an external distal side. The external proximate side is adapted to contact the fluid and is made of a material having a first stiffness. A second member has a first side and a second side. At least a portion of the second member is disposed within the first member. The first side of the second member is adjacent to the external proximate side of the first member and is made of a material having a stiffness which is greater than the first stiffness.
In alternative embodiments, the second member first side is in a generally parallel, spaced-apart relationship with the first member external proximate side.
In yet further embodiments, the first member external proximate side is made of an elastomeric material and the second member first side is made of stainless steel or plastic.
In yet further embodiments, the second member is substantially contained within the first member.
In yet further embodiments, the second member extends past the external proximate side of the first member and is adapted for contact with the fluid to complete the fluid-tight barrier within the reservoir.
In yet further embodiments, a method of coupling an actuator to a reservoir piston is provided. Electrical power is provided to a pump motor which is operably coupled to a plunger slide. The power is provided when the plunger slide is in a position other than fully inserted in a reservoir piston cavity. A first value corresponding to the axial force on the plunger slide is measured. A determination is made whether the first value exceeds a second value corresponding to the axial force on the plunger slide when the plunger slide is fully inserted in the piston cavity. Electrical power to the pump motor is terminated after determining that the first value exceeds the second value.
According to another embodiment of the invention, a reservoir for containing a fluid for infusion into a body of a patient includes a proximal end adapted to connect to an infusion set, a distal end, a cylindrical wall longitudinally extending from the proximal end to the distal end, and a piston adapted to be slidably mounted within the reservoir at the distal end. The piston forms a fluid tight seal in this embodiment and may be connected to a linear actuation member in particular embodiments. Additionally, the reservoir may be made from a cyclic olefin copolymer (COC) and, in some embodiments, the COC may be Topas®. In further embodiments, the reservoir may contain insulin. In additional embodiments, the piston may be formed from an elastomeric material. The material may be rubber, silicone, bromobutyl, natural synthetic isoprene, nitrile, and/or ethylene propylene diene monomers. In particular embodiments, the piston is made from a COC, and in further embodiments, the COC may be Topas®.
In other embodiments, the reservoir may further include a piston insert disposed within the piston. This piston insert may be made from metal or plastic. In additional embodiments, the piston may include elastomeric O-rings formed from materials including rubber, silicone, bromobutyl, natural synthetic isoprene, nitrile, ethylene propylene diene monomers or the like. In additional embodiments, the reservoir may further include a septum disposed in the proximal end and adapted to couple to the infusion set having a connector with a needle to pierce the septum.
In still further embodiments, the reservoir may be adapted to be placed inside an external infusion device including a drive system to operatively couple with the piston to infuse the fluid from the reservoir into the body, electronic control circuitry coupled to the drive system to control infusion of the fluid into the body, and a housing adapted for use on an exterior of the body. The housing may contain at least a portion of the reservoir, the piston, at least a portion of the electronic control circuitry, and the drive mechanism. In these embodiments, the infused fluid may be insulin. In other embodiments, the reservoir may be a pre-filled cartridge, and in particular embodiments the pre-filled cartridges may be made from Topas®. In still further embodiments, the reservoir may be formed to yield a breakage rate in the range of 0%−5% when subjected to a drop test from a height of 1 meter.
According to yet another embodiment, of the invention, an external infusion device for infusing a fluid into a body of a patient includes a reservoir to contain the fluid, a piston adapted to be slidably mounted within the reservoir, a drive system to operatively couple with the piston to infuse the fluid from the reservoir into the body, electronic control circuitry coupled to the drive system to control infusion of the fluid into the body, and a housing adapted for use on an exterior of the body. The housing may be sized to contain at least a portion of the reservoir, the piston, at least a portion of the electronic control circuitry, and the drive mechanism. The reservoir may be made from a cyclic olefin copolymer (COC), and, in some embodiments, may be adapted to connect to an infusion set. In alternative embodiments, the COC may be Topas®. In other embodiments, the infused fluid may be insulin. Additionally, the piston may be coupled to a linear actuation member. In still other embodiments, the reservoir may be a pre-filled cartridge, and in some embodiments, the pre-filled cartridge may be made from Topas®. In further embodiments, the reservoir may be formed to yield a breakage rate in the range of 0%−5% when subjected to a drop test from a height of 1 meter
In other embodiments, the piston may be formed from an elastomeric material including rubber, silicone, bromobutyl, natural synthetic isoprene, nitrile, ethylene propylene diene monomers or the like. The piston may also be made from a cyclic olefin copolymer (COC) including, but not limited to Topas®. In other embodiments, the external infusion device may further include a piston insert disposed within the piston. In these embodiments, the piston insert may be made from metal or plastic. In alternative embodiments, the piston may include elastomeric O-rings made from rubber, silicone, bromobutyl, natural synthetic isoprene, nitrile, ethylene propylene diene monomers or the like. In still other embodiments, the external infusion device may further include a septum disposed in the proximal end and adapted to couple to the infusion set having a connector with a needle to pierce the septum.
According to still another embodiment of the invention, a reservoir for containing fluid for infusion into a body of a patient includes a first end adapted to connect to an infusion set, a second end, and a piston adapted to be slidably mounted within the reservoir at the second end. The piston may include a piston insert and the reservoir may be adapted to be placed in an external infusion device. In this embodiment, the reservoir may be made from a cyclic olefin copolymer (COC). In some embodiments, the cyclic olefin copolymer may be Topas®. In still further embodiments, the reservoir may contain insulin. In other embodiments, the piston insert may be coupled to a linear actuation member. In additional embodiments, the piston insert may be made from metal or plastic.
In alternative embodiments, the piston may formed from an elastomeric material including rubber, silicone, bromobutyl, natural synthetic isoprene, nitrile, ethylene propylene diene monomers or the like. In other embodiments, the piston may be made from a cyclic olefin copolymer, and, in particular embodiments, the cyclic olefin copolymer may be Topas®. In other embodiments, the piston may include elastomeric O-rings made from rubber, silicone, bromobutyl, natural synthetic isoprene, nitrile, ethylene propylene diene monomers or the like. In additional embodiments, the reservoir may further include a septum disposed in the first end and adapted to couple to the infusion set having a connector with a needle to pierce the septum.
In still other alternative embodiments, the reservoir may be adapted to be placed inside an external infusion device including a drive system to operatively couple with the piston to infuse the fluid from the reservoir into the body, electronic control circuitry coupled to the drive system to control infusion of the fluid into the body, and a housing adapted for use on an exterior of the body. The housing may contain at least a portion of the reservoir, the piston, at least a portion of the electronic control circuitry, and the drive mechanism. In these embodiments, the infused fluid may be insulin. In other embodiments, the reservoir may be a pre-filled cartridge, and in particular embodiments the pre-filled cartridges may be made from Topas®. In still further embodiments, the reservoir may be formed to yield a breakage rate in the range of 0%−5% when subjected to a drop test from a height of 1 meter.
Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, various features of embodiments of the invention.
A detailed description of embodiments of the invention will be made with reference to the accompanying drawings, wherein like numerals designate corresponding parts in the several figures.
a is a perspective view of another conventional lead-screw drive mechanism.
b shows the details of a disposable reservoir with the piston and drive member withdrawn of the lead-screw drive mechanism of
a is a side plan, cut-away view of the drive mechanism of
b is a cut-away perspective view of the drive mechanism of
a, 10b and 10c are cross-sectional views of various embodiments of venting ports for use with the drive mechanism of
a and 13b are plunger slide force profile diagrams.
a is a perspective view of a reservoir piston.
b is an elevation view of the reservoir piston of
c is a cross-sectional view of the piston along lines 15c-15c of
a is a perspective view of a piston insert.
b is a top plan view of the piston insert of
c is a cross-sectional view of the insert along lines 16c-16c of
In the following description, reference is made to the accompanying drawings which form a part hereof and which illustrate several embodiments of the present inventions. It is understood that other embodiments may be utilized and structural and operational changes may be made without departing from the scope of the present inventions.
As shown in the drawings for purposes of illustration, some aspects of the present inventions are directed to a drive mechanism for an infusion pump for medication or other fluids. In preferred embodiments, a releasable coupler couples an in-line drive to a plunger or piston of a reservoir to dispense fluids, such as medications, drugs, vitamins, vaccines, hormones, water or the like. However, it will be recognized that further embodiments of the invention may be used in other devices that require compact and accurate drive mechanisms. Details of the inventions are further provided in U.S. Pat. No. 6,248,093 entitled “Compact Pump Drive System” and U.S. Provisional Patent application Ser. No. 60/106,237, filed Oct. 29, 1998, both of which are incorporated herein by reference in their entireties.
In addition, the reservoir piston includes features which provide greater stiffness against fluid back pressure thus reducing system compliance. The piston further includes a threaded attachment feature which permits a releasable yet secure coupling between the reservoir piston and the in-line drive.
As shown in the drawings for purposes of illustration, some aspects of the present inventions are directed to a drive mechanism for an infusion pump for medication or other fluids. In preferred embodiments, a releasable coupler couples an in-line drive to a plunger or piston of a reservoir to dispense fluids, such as medications, drugs, vitamins, vaccines, hormones, water or the like. However, it will be recognized that further embodiments of the invention may be used in other devices that require compact and accurate drive mechanisms.
In addition, other embodiments use a telescoping drive member (or lead screw) to minimize the packaging dimensions of the drive mechanism and the overall configuration of the medication pump. Still further, a ventilation feature using hydrophobic materials or a relief valve can be employed to equalized any pressure differentials which might otherwise exist between the atmosphere and the interior of the pump housing. As a back up to this ventilation feature, a threaded attachment permits a secure coupling between the reservoir piston and the in-line drive.
While certain embodiments of the present inventions are directed to disposable, pre-filled reservoirs, alternative embodiments may use refillable cartridges, syringes or the like. The cartridge can be pre-filled with insulin (or other drug or fluid) and inserted into the pump. Alternatively, the cartridge could be filled by the user using an adapter handle on the syringe-piston. After being filled, the handle is removed (such as by unscrewing the handle) so that the cartridge can be placed into the pump.
The pre-filled cartridges of the present embodiment may be made from different materials including glass, ceramic or the like. In other embodiments, the pre-filled cartridges may be made from cyclic olefin copolymers (COC). In particular embodiments the cyclic olefin copolymer is Topas®, produced by Ticona, a subsidiary of the Celanese Corporation. Topas® and/or COC possesses desirable characteristics for the long-term storage of insulin including, but not limited to, high transparency, high moisture barrier, high strength, high stiffness, low shrinkage and low warpage.
Additionally, Topas® and/or COC is more shatter resistant than glass, thus reducing potential pre-filled cartridge breakage rates. In particular embodiments, the pre-filled cartridges are placed inside an external infusion device of the type described in U.S. Pat. No. 6,554,798 entitled “External Infusion Device with Remote Programming, Bolus Estimator and/or Vibration Alarm Capabilities,” which is specifically incorporated by reference herein. These devices may be subjected to drop tests in accordance with IEC 60601-2-24 standards. This standard describes particular requirements for the safety of infusion pumps and controllers. According to the drop test requirements, an infusion pump is dropped on a 1″ thick wood surface (generally Red Oak) from a height of 1 meter. Further, the infusion pumps should be dropped on at least three sides (some tests have the infusion pumps dropped on all six sides). In these tests, glass has a breakage rate of approximately 21%. By using Topas® and/or COC, the breakage rate drops to 5% or lower. In still further embodiments, the breakage rate reduces to 0%. Topas® and/or COC can also be molded with much tighter tolerances than formed glass, resulting in a pre-filled cartridge with the potential for higher delivery accuracy and less of an offset that can be achieved with a glass pre-filled cartridge. Control of frictional characteristics is also enhanced by using Topas® and/or COC. Topas® and/or COC also provides for potentially longer shelf life than glass. The combination of clarity, moisture barrier, olefinic bio-inertness, shatter resistance, and more precise molding makes Topas® and/or COC a good material for the pre-filled cartridges. In other embodiments, the pre-filled cartridges made from Topas® and/or COC may be doped with a UV layer to provide additional protection from prolonged exposure to fluids, medications or the like, for example insulin.
In additional embodiments, the pre-filled cartridges may include a septum as described in U.S. patent application Publication No. 20030201239, entitled “Radially Compressed Self-Sealing Septum” filed on Apr. 25, 2002, which is specifically incorporated by reference herein. The septum may be used to serve as a closure on one end of the pre-filled cartridge, capable of being pierced by a sharp object such a hypodermic needle. The septum may be further adapted to self-seal when in a compressed state. The septum of these embodiments may be composed of an elastomer type material such as, but not limited to rubber, silicone, bromobutyl, natural synthetic isoprene, nitrile, ethylene propylene diene monomers, or the like.
Referring again to
An anti-rotation key 410 is affixed to the plunger slide 405 and is sized to fit within a groove (not shown) axially disposed in the housing 401. This arrangement serves to prevent motor and plunger slide rotation which might otherwise result from the torque generated by the motor 403 in the event that the friction of the O-ring seal 409 is not sufficient alone to prevent rotation.
The motor 403 is a conventional motor, such as a DC or stepper motor, and is journal mounted in the housing 401 by a system compliance mounting 412. A system compliance mount can be useful in aiding motor startup. Certain types of motors, such as stepper motors, may require a great deal of torque to initiate rotor motion when the rotor's initial at-rest position is in certain orientations with respect to the motor's housing. A motor which is rigidly mounted may not have enough power to develop the necessary starting torque. Including system compliance mounting permits the motor housing to turn slightly in response to high motor torque. This alters the orientation between the rotor and the housing such that less torque is required to initiate rotor motion. A compliance mount can include a rubberized mounting bracket. Alternatively, the mounting could be accomplished using a shaft bearing and leaf spring or other known compliance mountings.
The motor 403 may optionally include an encoder (not shown) which in conjunction with the system electronics can monitor the number of motor rotations. This in turn can be used to accurately determine the position of the plunger slide 405 thus providing information relating to the amount of fluid dispensed from the reservoir 406.
a and 7b show the infusion pump assembly with the plunger slide 405 in the fully extended position. In this position, the plunger slide 405 has withdrawn from over the gear box 501 and advanced into the reservoir 406 behind the reservoir piston assembly 407. Accordingly, the plunger slide 405 is sized to fit within the housing of the reservoir 406, such that when the reservoir piston assembly 407 and the plunger slide 405 are in the fully extended position as shown, the reservoir piston assembly 407 has forced most, if not all, of the liquid out of the reservoir 406. As explained in greater detail below, once the reservoir piston assembly 407 has reached the end of its travel path indicating that the reservoir has been depleted, the reservoir 406 may be removed by twisting such that the threaded reservoir piston assembly 407 (not shown in
In one embodiment, the motor drive shaft 432, gear box 501, drive screw 404, and plunger slide 405 are all coaxially centered within the axis of travel 440 (
An interior shaft 901 is rotated by a gear 906 which is coupled to a drive motor (not shown). This in turn extends a middle drive segment 902 by engaging with the threads of an internal segment 904. The middle segment 902 carries an outer segment 903 forward with it in direction d as it is extended to deliver fluid. When the middle segment 902 is fully extended, the internal segment 904 engages with a stop 905 on the middle segment 902 and locks it down from pressure with the threads between the middle and internal segments. The locked middle segment 902 then rotates relative to the outer segment 903 and the threads between the middle segment 902 and the outer segment 903 engage to extend the outer segment 903 in direction d to its full length.
The use of multiple segments is not limited to two or three segments; more may be used. The use of three segments reduces the length of the retracted lead-screw portion of the drive mechanism by half. In alternative embodiments, the outer segment may be connected to the motor and the inner segment may be the floating segment. In preferred embodiments, O-rings 907 are used to seal each segment relative to the other and to form a seal with the housing to maintain water sealing and integrity.
As previously noted, the construction of these pumps to be water resistant can give rise to operational problems. As the user engages in activities which expose the pump to varying atmospheric pressures, differential pressures can arise between the interior of the air tight/water-resistant housing and the atmosphere. Should the pressure in the housing exceed external atmospheric pressure, the resulting forces could cause the reservoir piston to be driven inward thus delivering unwanted medication. On the other hand, should the external atmospheric pressure exceed the pressure in the housing, then the pump motor will have to work harder to advance the reservoir piston.
To address this problem, a venting port is provided which resists the intrusion of moisture. Referring to
These materials are available in sheet form or molded (press and sintered) in a geometry of choice. Referring to
In an alternative embodiment (not shown), the vent port could be placed in the connector 431 which secures the reservoir 406 to the housing 401 and which also serves to secure and connect the reservoir 406 to the infusion set tubing (not shown). As described in greater detail in U.S. Pat. No. 6,585,695 entitled “Reservoir Connector”, which is specifically incorporated by reference herein, the connector and infusion set refers to the tubing and apparatus which connects the outlet of the reservoir to the user of a medication infusion pump.
An advantage of placing the vent port and hydrophobic material in this location, as opposed to the housing 401, is that the infusion set is disposable and is replaced frequently with each new reservoir or vial of medication. Thus new hydrophobic material is frequently placed into service. This provides enhanced ventilation as compared with the placement of hydrophobic material in the housing 401. Material in this location will not be replaced as often and thus is subject to dirt or oil build up which may retard ventilation. In yet another alternative embodiment however, vent ports with hydrophobic material could be placed in both the pump housing and in the connector portion of the infusion set.
Regardless of the location of the vent port, there remains the possibility that the vent port can become clogged by the accumulation of dirt, oil, etc. over the hydrophobic material. In another feature of certain embodiments of the present invention, the releasable coupler can act to prevent unintentional medication delivery in those instances when the internal pump housing pressure exceeds atmospheric pressure. Referring to
This thread engagement reduces or prevents the effect of atmospheric pressure differentials acting on the water resistant, air-tight housing 401 (not shown in
When the reservoir 406 is to be removed, it is twisted off of the coupler male portion 426. The system electronics then preferably cause the drive motor 403 to rapidly rewind so that the plunger slide 405 is driven into a fully retracted position (
In accordance with another feature of certain embodiments, the illustrated embodiment provides for advancement of the plunger slide 405 upon the insertion of a reservoir into the pump housing. The plunger slide 405 advances until it comes into contact with the reservoir piston assembly 407 and the threads of the coupler male portion 426 of the coupler engage the threads in the female portion 424 in the reservoir piston assembly 407. When the threads engage in this fashion in the illustrated embodiment, they do so not by twisting. Rather, they ratchet over one another.
In the preferred embodiment, the threads of the coupler male portion 426 have a 5 start, 40 threads per inch (“TPI”) pitch or profile while the threads of the coupler female portion 424 have a 2 start, 40 TPI pitch or profile as illustrated in
The purpose of this intentional cross threading is to reduce the force necessary to engage the threads as the plunger slide 405 seats into the reservoir piston assembly 407. In addition, the 2 start, 40 TPI threads of the coupler female portion 424 are preferably made from a rubber material to provide a degree of compliance to the threads. On the other hand, the 5 start, 40 TPI threads of the male coupler portion 426 are preferably made of a relatively hard plastic. Other threading arrangements and profiles could be employed resulting in a similar effect.
If on the other hand, the threads had a common thread pitch with an equal number of starts given the same degree of thread interference (i.e., the OD of the male feature being larger than the OD of the female feature), then the force needed to insert the male feature would be pulsatile. Referring to
While the advantage of utilizing a common thread pitch would be to provide a maximum ability to resist axial separation of the reservoir piston assembly 407 from the plunger slide 405, there are disadvantages. In engaging the threads, the peak force is high and could result in excessive delivery of fluids as the plunger slide 405 moves forward to seat in the cavity of the reservoir piston assembly 407. As described in greater detail in U.S. Pat. No. 6,362,591 entitled “Method and Apparatus for Detection of Occlusions,” which is incorporated by reference in its entirety, the pump may have an occlusion detection system which uses axial force as an indicator of pressure within the reservoir. If so, then a false alarm may be generated during these high force conditions.
It is desirable therefore to have an insertion force profile which is preferably more flat than that shown in
When the plunger slide is fully inserted into the reservoir piston, the slide bottoms out in the cavity of the piston. At this point the presence of the hydraulic load of the fluid in the reservoir as well as the static and kinetic friction of the piston will act on the plunger slide.
The fluid pressure and occlusion detection systems described in U.S. Provisional Patent application Ser. No. 60/243,392, filed Oct. 26, 2000 or in U.S. Pat. No. 6,362,591 entitled “Method and Apparatus for Detection of Occlusions,” (both of which are incorporated herein by reference in their entireties) or known pressure switch detectors, such as those shown and described with reference to
Referring to
The 2 start thread profile of the coupler female portion 424 on the reservoir piston assembly 407 of the preferred embodiment provides another advantage. Some versions of these reservoirs may be designed to be filled by the user. In such an instance, a linear actuation member comprising a handle (not shown) will need to be screwed into the threaded portion of the reservoir piston assembly 407 in order for the user to retract the reservoir piston assembly 407 and fill the reservoir. The number of rotations necessary to fully insert the handle depends upon the distance the handle thread profile travels to fully engage the reservoir piston assembly 407 as well as the thread lead.
For example, a single start, 40 TPI (0.025″ lead) thread requires 4 complete rotations to travel a 0.10″ thread engagement. However, a 2 start, 40 TPI (0.050″ lead) thread only requires 2 complete rotations to travel the 0.10″ thread engagement. Therefore, an additional advantage of a 2 start thread as compared to a single start thread (given the same pitch) is that half as many rotations are needed in order to fully seat the handle.
In alternative embodiments which are not shown, the end of the plunger slide 405 may include a detente or ridge to engage with a corresponding formation in the reservoir piston assembly 407 to resist unintended separation of the plunger slide 405 from the reservoir piston assembly 407. In other embodiments, the plunger slide 405 is inserted and removed by overcoming a friction fit. Preferably, the friction fit is secure enough to resist movement of the reservoir piston assembly 407 relative to the plunger slide 405 due to changes in air pressure, but low enough to permit easy removal of the reservoir 406 and its reservoir piston assembly 407 from the plunger slide 405 once the fluid has been expended. In other embodiments, the detente or ridge may be spring loaded or activated to grasp the reservoir piston assembly 407 once the drive mechanism has been moved forward (or extended), but is retracted by a switch or cam when the drive mechanism is in the rearmost (or retracted) position. The spring action could be similar to those used on collets. In other embodiments of the inventions, the threaded coupler may be engaged with the threaded cavity of the reservoir piston by twisting or rotating the reservoir as it is being manually placed into the housing.
As previously mentioned, some pump systems may have an occlusion detection system which uses the axial force on the drive train as an indicator of pressure within a reservoir. One problem faced by such occlusion detection systems, however, is the system compliance associated with reservoir fluid back pressures. As previously mentioned, the force on a piston assembly resulting from increased back pressures can deform a piston which is constructed of relatively flexible material such as rubber. Should an occlusion arise in the fluid system, this deformation can reduce the rate at which fluid back pressures increase. This in turn can increase the amount of time required for the system to detect an occlusion—a situation which may be undesirable.
To address this problem, an insert 1201 which is made of hard plastic, stainless steel or other preferably relatively stiff material is disposed in the upper portion of the reservoir piston assembly 407. (
a and 15b show the piston member 1404 which is adapted to receive the insert 1201 (
Referring to
The first chamber 1508 is defined by a generally cylindrically-shaped first wall 1511 extending axially from the external distal side 1505 into the cavity 424. The first wall 1511 includes threads 1504 formed on the wall which are adapted to couple with any linear actuator member, such as for example, the threads of the male portion 426 of the plunger slide 405 as previously described (
Referring to
The face portion 1601 and the end portion 1604 are adapted to mate with the internal proximate wall 1510 and the back wall 1602 is adapted to seat against the ledge 1513 of the piston member 1404 (
It should be appreciated that although the insert member 1201 depicted in
The insert member of the above-described embodiments is not adapted to contact the fluid in a reservoir. However,
The insert 1803 is substantially contained within the piston member 1802 and has a face 1806 which is made of a material, such as stainless steel or hard plastic, having a stiffness which is greater than that of the piston member 1802. The insert face 1806 has an exposed portion 1807 and an enclosed portion 1808. The exposed portion 1807 is adapted to contact the fluid within the reservoir whereas the enclosed portion 1808 is enclosed or covered by the external proximate side 1804 of the piston member 1802. Therefore, the insert 1803 extends past the external proximate side of the piston member 1802 and is adapted for contact with the fluid to complete the fluid-tight barrier within the reservoir. Thus the arrangement of the insert 1803 in this fashion provides the necessary stiffness to the piston assembly 1801 to reduce system compliance.
It should be appreciated that while the piston members and inserts described above include conical geometries, other geometries can be used. For example in an alternative embodiment shown in
In yet further embodiments (not shown), an insert member is an integral part of a male portion of a plunger slide assembly which is adapted to fit within a piston assembly cavity. The male portion of the slide assembly (i.e., the insert member) is further adapted to abut an internal proximate wall within the cavity thus providing increased stiffness to that portion of the piston assembly which is in contact with reservoir fluid. In alternative embodiments, the piston may include O-rings made from different elastomeric materials as described above. In these embodiments, the piston may be made from cyclic olefin copolymers. In particular embodiments, the cyclic olefin copolymer may be Topas®. In other embodiments, the piston may be made from different elastomeric materials and/or combinations of materials including, but not limited to, rubber, silicone, bromobutyl, natural synthetic isoprene, nitrile, ethylene propylene diene monomers, or the like.
It can be appreciated that the design of
While the description above refers to particular embodiments of the present inventions, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present inventions. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the inventions being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
This is a continuation-in-part application of U.S. patent application Ser. No. 10/699,429 filed on Oct. 31, 2003, which is a divisional application of U.S. patent application Ser. No. 09/698,783, filed Oct. 27, 2000, now U.S. Pat. No. 6,800,071, which is a continuation-in-part application which claims priority from U.S. patent application Ser. No. 09/429,352, filed Oct. 28, 1999, now U.S. Pat. No. 6,248,093, which claims priority on U.S. Provisional Patent application Ser. No. 60/106,237, filed Oct. 29, 1998.
| Number | Date | Country | |
|---|---|---|---|
| 60106237 | Oct 1998 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09698783 | Oct 2000 | US |
| Child | 10699429 | Oct 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10699429 | Oct 2003 | US |
| Child | 11100188 | Apr 2005 | US |
| Parent | 09429352 | Oct 1999 | US |
| Child | 09698783 | Oct 2000 | US |
